Cooling system for aircraft engines



May 22, 1951 H. J. RAPUANO 2,553,675

coouuc SYSTEM FOR AIRCRAFT ENGINES Filed March 29, 1946 a Sheets-Sheet 1 IN V EN TOR. Henry J. ka ouanqlkcd BY 5) 70145 H. Fapuawo, Adm'x ATTORNEY May 22,1951 H. .1. RAPUANO COOLING SYSTEM FOR AIRCRAFT ENGINES 3 Sh'eets-Sheet 2 Filed March 29, 1946 INVENTOR Hen/y J. RII/JH anofietd 5 yl70r/5 hf Ra (/4710 14 111 BY 7 7 fi. M

ATTORNEY May 22, 1951 H. J. RAPUANO coouuc SYSTEM FOR AIRCRAFT mamas 3 Sheets-Sheet 5 Filed March 29, 1946 5 mm R IN V EN TOR.

Henry J ka puanopecd BY- Dari: H.1iapL/ano, Ad BY 7- 6, 0%

A T TORNE' Y Patented May 22, 1951 COOLING SYSTEM FOR AIRfiRAFT ENGINES tion of Delaware Application March 29, 19%6, Serial N o. 658,260

13 Claims. 1

This invention relates to improvements in cooling systems for aircraft engines.

An'object of the invention is to provide automatic means for maintaining the quantity of air discharged by an engine cooling fan for any given throttle setting substantially constant at all altitudes of flight.

Another object of the invention is to provide an engine cooling fan having blades of the controllable pitch type which are adjusted automatically by atmospheric pressure responsive means.

A further object of the invention is to provide improved mechanism for the support and control of the blades of a controllable pitch cooling fan.

These and other objects and advantages of the invention will appear more fully from the detailed description of one embodiment of the invention illustrated in the accompanying drawings.

In these drawings,

Fig. 1 is a perspective view of the forward portion of the airplane with the engines and the associated cooling means of. the invention indicated diagrammatically in dotted lines;

Fig. 2 is a perspective view on a larger scale of an engine cooling fan and its control mechanism with portions thereof broken away; and

Fig. 3 is a view on a still larger scale of the hub structure of the fan and the atmospheric pressure responsive mechanism for controlling the pitch of the fan blades, parts being broken away to facilitate illustration.

The invention is illustrated in a low aspect ratio, all-wing airplane generally indicated as Ill. The airplane has a central pilot compartment l2 projecting forwardly of the leading edge of the wing and two oppositely rotating propellers 14 mounted in propeller nacelles E5 projecting forwardly from the leading edge at the lateral extremities of the wing and driven by engines l8, herein shown as of the radial cylinder, aircooled type. The engines 88 are located considerably aft of the leading edge of the wing in engine nacelles 28 extending fore and aft in the wing on opposite sides of the pilot compartment [2 well inboard of the propellers and having forward axial air inlet openings 22 through which air is inducted by engine driven fans is, one of which is disposed forward of each engine l8.

The fans 24 are of the controllable pitch type, each having an annular hub 2i; and a plurality of radially extend-ed fan blades 28 mounted in the hub for pitch changing movement about their radial axes in response to pressure changes offecting an atmospheric pressure responsive bellows 39 which controls the energlzation of a reversible electric motor 32 for actuating the pitch changing mechanism or the fan blades 28.

Referring to Figs 2 and 3, the annular blade supporting hub 26 of the fan is secured by-b'olts 3a to the flanged rim S6 of a radial web it integrally united, as by welding, to an outer hollow shaft it. The shaft 46 is supported on an inner hollow drive shaft 42, the shafts all and 42 having'a splined connection at their forward ends. The shaft 12 extends aft of the fan and has a splined driving connection (not shown) to the crankshaft oi engine it. Immediately forward of the hub 25 and mounted on bearings :34 and $5 on the rotating structure above described is a generally cylindrical stationary supporting structure ii! which carries the bellows 3E! and motor 32 and has an integral annular supporting flange 53.

The annular hub 2% of the fan has twentyfour equally spaced, internally threaded radial sockets 5i therein which are drilled approximately two thirds of the way therethrough and communicating stepped passages cm of increasing diameter which extend completely through the hub in-which the blades of the fan are supported for pivotal movement about their radial axes on an inner radial tube 52 to the lower end of which is secured a cylindrical stepped fitting 53 provided with a lower externally threaded extremity 54. Secured to the upper end of tube 52-is a blade rib 56 which has an annular lower socket portion fiilreceiving the upper endoi tube 52. The blades 23 are of rolled metal construction, each having a second rib til at its outer end. The rolled metal of the blade is welded to the two ribs 5t and 6%] and the socket 58 is riveted to the tube 52 so as to form a permanent blade assembl with the tube.

Each blade assembly is supported adjacent the base of its blade 28 in the right angle flange 62 of an annular bailie plate li i which provides a radially extended partition from the hub 28 to the base of the blades. To this end, a flanged tubular sleeve tit having resilient fingers 68 which irictionally engage the external surface of tube 52 has its flange ill riveted to the flange 62 about the opening it in the latter through which the tube 52 extends. The purpose of the spring fingers 68 is to resist the rotation of the blade about its axis and thus provide suflicient friction damping to prevent flutter of the blades. The tubular sleeve 58 has an externally threaded portion beneath its flange ill on which is threaded an outer tube M having its upper extremity abutting the flange 19 on the upper end of sleeve 65. The tube 75 also has an externally threaded lower end which is threaded into the threaded socket in the hub structure 25, a shoulder on this outer tube abutting the periphery of the annular hub 26. A clip I8 is provided about several of the outer tubes HI intermediate their ends for securing plate 6 5.

Each blade assembly is inserted through a socket 5! with its stepped fitting 53 extending through the stepped passage em in the hub 26. A ball bearing to bears against an inwardly facing shoulder on the stepped fitting 53 and a corresponding shoulder on the stepped passage em and is held in place on the fitting 53 by a flange 82 on a torque lever 33 and a nut 85 threaded onto the extremity 54 of the fitting.

The torque lever 83 also has a flange 84 carry ing a depending pin 3% which is eccentrically located relative to the axis of the blade assembly, the lowermost portion of which is drilled upward from the bottom and contains a cylinder of oil absorbent felt therein.

The pins 85 of all the blade assemblies are received in the annular channel 88 (Fig. 3) of a blade actuating sleeve so which is splined to shaft fill so as to permit axial movement of the sleeve relative to the shaft for the purpose of actuating all the blades in unison through the medium of their torque levers. The channel 88 is formed by an upstanding annular flange 92 on the flange 54 of sleeve 99 and an annular flange 96 which is secured to flange 54 by special bolts 98 these bolts having elongated guiding shanks Hill which extend through the flange 33 of shaft in 49. The sleeve 98 carries the race I82 of a ball bearing forward of its flange 94, the other race I04 of which is carried by an annular overhanging sleeve use of the relatively stationary hub structure. While this hub structure including sleeve I96 does not rotate at fan speed it is rotatably mounted on shaft 43 and sleeve 9% for a predetermined rotary movement to adjust the pitch of the fan blades, as will hereinafter be made clear. The race IE2 is held against axial thrust by a nut I138 against a shoulder I i I while the race I94 is similarly held by a nut i 52 against a shoulder I54 on the sleeve I86. The sleeve N36 has integral therewith a forward oblique portion I I5 carrying an external radial flange i I5 intermediate thereof and a tubular sleeve portion I I 8 which forms the forward bearing for sleeve its on the external surface of shaft The sleeve H8 has an externally screw-threaded portion I cooperating with an internally threaded portion I22 of an annular stationary structure I24 which surrounds the shaft ii and constitutes a support for the bellows 3B and motor 32.

The sleeve I95 has a spur gear I26 formed integral therewith which meshes with a smaller diameter, elongated spur pinion 28 on a shaft I30 car *ied by the fixed structure #24. The shaft I38 carries a large spur gear E32 which meshes with a small spur pinion 34 on the shaft of motor 32. The motor 32, which is of the reversible type, is thus operatively connected to rotate the sleeve H35 in opposite directions and hence by reason of its screw-threaded connection with the stationary structure E24 to reciprocate sleeve I66 and with it the rapidly rotating sleeve 99 which controls the lever assemblies of the blades.

The bellows St is rigidly supported at one of its ends on the supporting flange so and carries at its opposite and forward end an axial bellows shaft I36 having an intermediate screw-threaded portion I38 and a reduced unthreaded portion Hill which is slidable in an apertured support M2 carried by the rigid structure I25. A compression spring i 5 has its forward end abutting support I i; and its aft end abutting a washer i 36 which is adjustable along the threaded portion 138 of the bellows shaft by a nut MB. A pair of electric switches I and i552 having opposed operating members led and l56 are supported on the stationary supporting structure I24. These switches are adapted to be operated by a switch arm IE3 which is pivoted at I58 and which has a yoke F62 at its free end received between spaced flanges 154 on the bellows shaft I36. The lever 653 carries aroller let which is disposed between the opposed switch operating members I54 and tilt so that upon the expansion of the bellows 3!! the lever I53 will move about its pivot I553 to operate switch I52 while contraction of the bellows will cause the roller to engage and operate the switch i5il. Current is supplied from line I68 through the switches IEii and I52 to the terminals Iii of the reversible electric motor 32 in a well-known manner so that closing of switch I59 will cause the motor to rotate in one direction while closing of the switch 552 will cause it to rotate in a reverse direction.

The pivot point its for lever E58 extends through a shaft I72 of a follow-up mechanism, the forward end I'i-i of which is guided in a bracket I'ifi carried by the fixed structure I241 and the aft end of which extends through aligned passages i'iB and 89 in the fixed structure I24. The aft end of rod H2 has an annular channel I I! within which the upstanding flange i !8 of sleeve M35 is received so that the follow-up rod is moved axially with the sleeve Hi6 while permitting the latter to be rotated in opposite directions by the motor 32.

It will be evident that the expansion of bellows 3*? causes the switch I52 to be closed whereupon the motor 32 is operated to rotate the sleeve are in a direction to cause the threads M3 to move the sleeve axially in a forward direction to increase the angle of incidence of the fan blades 2%. Similarly contraction of bellows 36 will cause switch iiifi to be operated which energizes the motor 32 in a reverse direction to decrease the angle of incidence of the fan blades It will also be evident that any movement of. the sleeve I538 will result in an axial movement of the follow-up shaft I72 in the same direction or" movement until the wheel I68 is again centered between the operating plungers I 5% and IE6 of the two switches Ibo and I52. Thus an increment of movement of the bellows 38 results in a proportionate movement of the blade pitch adjusting mechanism after which the motor 32 is deenergized. Thus as changes in altitude of the airplane are reflected in the expansion or the contraction of the bellows 3b, the pitch of the blades 28 are correspondingly changed so as to discharge the same quantity of air by weight through the engine nacelles for any given throttle setting of the engines. The bellows 36 contains a suitable gas which expands and contracts with temperature changes in the surrounding atmosphere as is usual in such atmospheric pressure responsive bellows.

As a result of this invention it is possible to control the cooling of the engines of the airplane so that adequate cooling is obtained at high altitudes where the density of the air is low and consequently a greater volume of air must be moved by the fan, while preventing over-cooling of the engine at lower altitudes. Thus better cooling is provided while a more efficient utilization of engine power is also made possible. Further, as a result of this invention it is made possible to adequately cool a low-aspect ratio all-wing airplane in which there is wide varia tion in flight attitude. It will further be evident that a particularly simple blade assembly for a controllable pitch blade has been provided as well as a rugged, trouble-free mechanism for adjusting the pitch of the fan blades in response to pressure changes due to variations in altitude.

While only one embodiment of the invention has been shown in the accompanying drawings, it will be evident that various changes may be made in the construction and arrangement of the parts without departing from the scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent 1. Axial fiow fan apparatus comprising, an enclosure, a fan for moving cooling air through said enclosure, said fan having a hub structure and a plurality of radial blades mounted in said structure for adjustment about their longitudinal axes to vary the volume of air moved by said fan at a given setting of the engine throttle, means for adjusting said blades about their axes including two cooperating elements, one being rotatable with said hub structure and the other being relatively stationary with respect thereto and having a toothed periphery, said elements being mounted for axial movement relative to said shaft and one having an operative connection with said blade adjusting means for adjusting said blades in opposite directions upon axial reciprocation of said other element, means for reciprocating said elements including a gear train operatively connected to said toothed periphery of said relatively stationary element, and an atmospheric pressure responsive expansible and contractable member for actuating said reciprocating means.

2. Axial flow fan apparatus comprising, an enclosure, a fan for moving cooling air through said enclosure, said fan having a hub and a plurality of blade assemblies mounted in said hub for pitch changing movement about radial axes extending from said hub, each of said blade assemblies ha ing an eccentric operating member for adjusting its blade about its axis, and mechanism for operating all of said operating members in unison including an annular member rotatable with said hub and having an operative connection with said operating members, a relatively stationary member adjacent said annular member having an operative connection thereto, a reversible electromotive means operatively connected to said relatively stationary member for moving the latter axially, atmospheric pressure responsive means, means controlled by said pressure responsive means for energizing said electromotive means, and means controlled by the movement of said relatively stationary member for de-energizing said electromotive means.

3. A combination as defined in claim 2 in which the annular operating member is reciprocable along the axis of the fan hub and has an annular groove in which the operating members for the several blade assemblies are received.

4. Axial flow fan apparatus comprising, a fan enclosing structure, a drive shaft extending fore and aft in said structure, a concentric fan supporting shaft supported on said drive shaft and having a driving connection therewith, a fan hub structure carried by said concentric shaft having radially mounted blade assemblies carried thereby, each of said assemblies having an eccentric blade operating member for adjusting its blade about its radial axis, and blade adjusting mechanism common to all of said assemblies slidably mounted on said concentric shaft including an element rotatable with said hub and having an operative connection with said blade operating members and a cooperating relatively stationary element having a toothed periphery and operatively connected with said first element, and means carried by said enclosing structure for re ciproeating said relatively stationary element axially of said shaft for effecting simultaneous adjustment of the blades of said fan including a gear train operatively connected with the toothed periphery of said relatively stationary element.

5. Axial flow fan apparatus comprising, a fan enclosure, a shaft extending fore and aft in said enclosure, a fan in said enclosure having a hub concentric with and rotatable about the axis of said shaft and having a plurality of radial blade assemblies mounted in said hub for pitch changing movement about said radial axes, each of said assemblies having a blade operating member for adjusting its blade about its axis, means for supporting said fan from said enclosure including a stationary fan supporting structure concentric with said shaft, and cooperating blade actuating mechanism located between said concentric supporting structure and said hub for operating said operating members in unison to adjust the pitch of said blades including two cooperating elements, one of said elements being rotatable with said hub and having a sliding support axially of said shaft and said other element being concentric therewith and being threaded to an internal surface of said stationary supporting structure whereby rotation of said relatively stationary element results in axial movement thereof, and means carried by said supporting structure for effecting rotational movement of said relatively stationary element.

6. An engine cooling fan including a hub and a plurality of radial blade assemblies mounted in said hub for pitch changing movement about said radial axes, each of said assemblies including an axial member journalled in said hub having a blade at its free end, means carried by said hub for supporting said blade assemblies adjacent the base of said blades, and means carried by said supporting means and biased into engagement with said axial members for frictionally damping movements of said blades about their axes.

'7. A cooling fan including a hub and a plurality of radial blade assemblies mounted in said hub for pitch changing movement about their radial axes, each of said assemblies including an axial member journalled in said hub having a blade at its free end, and radially extended means carried by said hub for supporting said blades adjacent their bases, said supporting means including an annular flange through which said lade assemblies extend and said flange having tubular sleeves provided with resilient fingers for frictionally engaging and damping movements of said blades about their axes.

8. A fan apparatus including an enclosure for defining a gaseous fiuid passage, an engine driven shaft extending longitudinally in said enclosure, a fan mounted on said shaft, said fan having a hub structure and a plurality of radial blades mounted in said structure for adjustment about their longitudinal axesto vary the volumeof air moved by said fan, means for adjusting said blades about their axes'including cooperating elements, one of which is rotatable with said hub structure and has an operative connection with said blades and the other of which is normally stationary relative to said rotatable element, said elements having an operative connection with each other by which movement of said relatively stationary element is transmitted to said rotatable element to operate said blades, and atmospheric responsive means including a driving means and a gear train driven thereby operatively connected to said relatively stationary element for adjusting the latter in accordance with variation in the density of the air entering said enclosure.

9. A fan apparatus as defined in claim 8 Wherein the hub structure contains blade mounting means including a tubular sleeve with tapered resilient fingers for 'frictionally engaging and damping movement of said blades about their axes.

10.'A fan apparatus as defined in claim 8 wherein the relatively stationary element is threaded to an internal surface of a concentric rigid mounting structure so that rotation of said relatively stationary element results in reciprocal movement thereof and such movement is transmitted to the rotating element for changing the pitch'of the fan blades.

11. An engine cooling fan including a hub and a plurality of radial blade assemblies mounted in said hub for pitch changing movement about their radial axes, radially extended tubular members carried by said hub for supporting. said assemblies, an annular flange spaced from said hub through which said assemblies extend, said assemblies comprising blade shanks extending through said tubular members and'journaled in said hub and blades extending radially outwardly from said flange, and'resilient means carried by said flange and extended between said tubular members and said blade shanks for frictionally engaging the latter and damping movements of said blade assemblies about their axes.

12."A combination as'claime'd in claim 11 in which the annular flange is supported by the ends of the tubular members and is spaced a substantial. distance from'the'hub and comprises a g bafilebetweenthe baseuofthe blades and the hub carried tubular members.

13. A fan apparatus including an enclosure for. defining a gaseous fluid passage, an engine driven shaft extending longitudinally in said enclosure, a fan mounted on said shaft, said fan having a hub structure and a plurality of radial blades mounted in said structure for adjustment about their longitudinal axes to vary the volume of air moved by said fan, means for adjusting said blades about their axes including cooperating elements, one of which is rotatable with said nub structure and has an operative connection with said blades and the other of which is normally stationary relative to said rotatable element, said elements having an operative connection with each other by which movement of said relatively stationary element is transmitted to said rotatable element to'operate said blades,

a reversible electromotive means, a gear trainadapted to be driven by said electromotive means and operatively connected to said relatively stationary element, an atmospheric pressure responsive means, and means controlled by the expansion and contraction of said last mentioned means for energizing said electromotive means.

DORIS H. RAPUANO.

Administratrix of the Estate of Henry J. Rapuano, Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,327,381 Furber Jan. 6, 1920 1,420,619 Barton June 27, 1922 1,509,286 Colly Sept. 23, 192% 1,761,690 Steinmetz June 2, 1930 1,787,041 Hughes Dec. 30, 1930 1,830,858 Schoepp et al Nov. 10, 1931 1,857,392 Nixon May 10, 1932 2,081,762 Nissen May 25, 1937 2,284,938 Allen June 2, 1942- FOREIGN PATENTS Number Country Date 302,097 Great Britain Dec. 13, 1928 

